Mosquitoes-to-human attraction identified

DAVIS, Calif., Oct. 27 (UPI) -- U.S. scientists say they have identified the dominant chemical naturally produced by humans that attracts some mosquitoes to people.

University of California-Davis researchers said they discovered the odor naturally produced in humans and birds that attract the blood-feeding Culex mosquitoes, which transmit West Nile virus and other life-threatening diseases. The scientists said their findings explains why mosquitoes shifted hosts from birds to humans and paves the way for key developments in mosquito and disease control.

Entomology Professor Walter Leal and postdoctoral researcher Zain Syed said they found the semiochemical, nonanal, triggers the mosquitoes' keen sense of smell, directing them toward a blood meal.

A semiochemical, the researchers explained, is a chemical substance or mixture that carries a message.

"Nonanal is how they find us," Leal said. "The antennae of the Culex quinquefasciatus are highly developed to detect even extremely low concentrations of nonanal."

Birds, the main hosts of mosquitoes, serve as the reservoir for the West Nile virus, Leal said. When infected mosquitoes take a blood meal, they transmit the virus to their hosts, which include birds, humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels and domestic rabbits.

The research appears in the early online edition of the Proceedings of the National Academy of Sciences.